Re: [PATCH v2 1/3] drivers/bus: Add Legacy PM OPS usage check andwarning to bus_register()

[Shuah Khan]

On 01/06/2014 02:29 PM, Greg KH wrote:
> On Mon, Jan 06, 2014 at 01:30:31PM -0700, Shuah Khan wrote:
> > On 01/06/2014 01:17 PM, Greg KH wrote:
> > > On Mon, Jan 06, 2014 at 01:03:21PM -0700, Shuah Khan wrote:
> > > > Add Legacy PM OPS usage checks to bus_register() function. If Legacy PM OPS
> > > > usage is found, print warning message to indicate that the driver code needs
> > > > updating to use Dev PM OPS interfaces. This will help serve as a way to track
> > > > drivers that still use Legacy PM OPS and fix them.
> > > >
> > > > The Legacy PM OPS check looks for suspend(struct device *, pm_message_t) or
> > > > resume(struct device *) bus level interfaces.
> > > >
> > > > Signed-off-by: Shuah Khan <shuah.kh@xxxxxxxxxxx>
> > > > ---
> > > >   drivers/base/bus.c | 3 +++
> > > >   1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> > > > index 73f6c29..e8753a7 100644
> > > > --- a/drivers/base/bus.c
> > > > +++ b/drivers/base/bus.c
> > > > @@ -916,6 +916,9 @@ int bus_register(struct bus_type *bus)
> > > >   		goto bus_groups_fail;
> > > >
> > > >   	pr_debug("bus: '%s': registered\n", bus->name);
> > > > +	if (bus->suspend || bus->resume)
> > > > +		pr_warn("bus '%s' needs updating - use pm pointer.\n",
> > > > +			bus->name);
> > >
> > > Why can't we just sweep the tree for all of these now, fix them up, and
> > > then delete these fields and be done with it?
> > >
> > > Same for the other ones, putting warnings in the kernel log files
> > > doesn't work at all for getting people to fix up their code (see
> > > examples of scsi log messages being there for _years_ about obsolete
> > > driver interfaces being used.)
> >
> > This change is not a simple case of replacing legacy with pm ops. I have
> > been working on changing drivers that use legacy, in some cases it is an
> > easy change, however in some cases it requires adding new interfaces to port
> > over from legacy to pm ops. Legacy suspend/resume is more course grain and
> > pm ops offer fine grain control over suspend, hibernate etc. Also it has
> > been a challenge without the hardware to test.
> >
> > My thinking is adding warning might get the attention of individual driver
> > owners.
>
> If it's not a trivial change, and takes a lot of work by someone who
> knows this type of thing (i.e. you), then I wouldn't start making kernel
> log warnings about this, it's just going to annoy a bunch of people :)

ok I will continue fixing the drivers. :)

> Again, see the SCSI log warnings for examples of this, people just tune
> them out, assuming someone else is going to fix the issue, someday.  And
> that someday never comes...

Yeah. Warnings could just get ignored.

-- Shuah

--
Shuah Khan
Senior Linux Kernel Developer - Open Source Group
Samsung Research America(Silicon Valley)
shuah.kh@xxxxxxxxxxx | (970) 672-0658
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/